Tube reducing apparatus and method



Nov. 16, 1965 E. D. DILLING 3,217,521

TUBE REDUCING APPARATUS AND METHOD Filed Dec. 22, 1961 2 Sheets-Sheet l INVENTOR. FIG. 2 Elmer 0. Dilling Agent Nov. 16, 1965 E. D. DlLLlNG TUBE REDUCING APPARATUS AND METHOD 2 Sheets-Sheet 2 Filed Dec. 22. 1961 INVENTOR. Elmer D. Dilling Agent United States Patent Office 3,217,521 Patented Nov. 16, 1965 3,217,521 TUBE REDUCING APPARATUS AND METHOD Elmer D. Dilling, Las Vegas, Nev., assignor to Titanium Metals Corporation of America, New York, N.Y., a corporation of Delaware Filed Dec. 22, 1961, Ser. No. 161,721 6 Claims. (Cl. 72-77) This invention relates to apparatus and process for tube reducing and more particularly for reducing the wall thickness or internal diameter of metallic tubing, or reducing wall thickness and internal diameter simultaneously and at the same time producing a change in the concentricity of such tubing.

In the manufacture of metallic tubing, tube reducing machines of various types are employed to reduce the wall thickness or internal diameter of a blank or workpiece tube. In commercial operations the workpiece tube will substantially never be perfectly concentric, that is, the internal surface concentric with respect to the external surface. Yet as high a degree of concentricity is desirable in most ordinary tubing applications since variations of wall thickness over the diameter of the tubing inevitably results in a thin side and a thick side with resultant variation in properties such as strength, formability and heat transfer. In tube reducing operations, it is extremely advantageous therefore to be able to improve the concentricity of an eccentric workpiece tube. Additionally, for some special purposes it may be useful to be able to change the concentricity of a workpiece tube to make it more eccentric.

It is therefore a principal object of this invention to provide a method for changing or improving the concentricity of a workpiece tube during reduction thereof. Another object of this invention is to provide tube reducing apparatus capable of reducing the wall thickness or the internal diameter, or both simultaneously, of a workpiece tube and at the same time changing the concentricity of such tube. Another object of this invention is to provide tube reducing apparatus capable of improving the concentricity of an eccentric workpiece tube. These and other objects of this invention will be apparent from the following description thereof and the annexed drawings in which:

FIG. 1 shows a sectional view of tube reducing appartus embodying features of this invention.

FIG. 2 shows a cross section of the apparatus of FIG. 1 taken along the line 2-2.

FIG. 3 shows a cross section taken along the line 33, and appreciably enlarged, of a tube reduced according to this invention and having improved concentricity.

FIG. 4 shows a cross section taken along the line 4-4 and appreciably enlarged, of the tube before reduction and having a substantial degree of eccentricity.

FIG. 5 shows a general side view, partly broken out, of a tube reducing machine, including the apparatus of FIG. 1.

Referring now to FIGS. 1 and 2, the apparatus illustrated comprises an annular outer frame which is provided with a pair of partial circular bores 12 and 14 which are drilled or otherwise formed in opposite sides of outer frame 10 and which are eccentric with respect to the outer circumference of frame 10, the eccentricity of these partial bores 12 and 14 being diametrically opposite one to the other. Adjustably mounted in bores 12 and 14 are annular inner frames in the form of rings 16 and 18 which are characterized by circular bores 20 and 22 which are eccentric with respect to the outer circumferences of inner frames 16 and 18. Annular inner frames 16 and 18 may be rotated inside bores 12 and 14 respectively to adjust their relative positions and when set as desired, may be maintained in such adjustment by locking means such as set screws 24 set in from the outer edge of outer frame 10.

Mounted in inner frame bores 20 and 22 are bearing assemblies 26 and 28 whose outer races are fitted into bores 20 and 22 respectively and inside whose inner races are fitted circular working elements which in the embodiment illustrated are working rings 30 and 32. Collar 34, threaded onto the end of working ring 30, and being maintained in tight position by lock ring 36, maintains working ring 30 and the adjacent race of bearing 26 in relative position. Hollow shaft 38, fastened onto the end of frame 10 as by long bolts which pass through the assembly, maintains the relative position of outer frame ring 10, inner frame ring 16 and bearing 26.

Working ring 32 is maintained in position in the inner race of bearing 28 by collar 42 threaded thereon; this collar being maintained tight by lock ring 44. End ring 46 is bolted to outer frame 10 by bolts 40 to maintain bearing 28, inner frame ring 18 and outer frame ring 10 in relative position. Bolted onto the end of ring 46 is extension ring 48 whose internally projecting flange 50 maintains bearing 52 in position supported partially in the end of ring 46. Bearing 52 is of a type commercially known as a self-aligning anti-friction bearing and is provided with rollers which may travel around and also somewhat angularly in a transversely arcuate outer race 54. The inner race 56 of bearing 52 is mounted on collar 58 which is fitted onto a generally tubular biasing element 60. Threaded onto collar 58 and maintained in set position thereon by locking ring 62 is handle ring 64 from which project arms 66. Clamping ring 68 is also threaded onto collar 58 to maintain biasing element in set position on collar 58 substantially as shown.

Biasing element 60 is hollow and designed to have an internal diameter somewhat larger than the outside diameter of a workpiece tube 70 which it surrounds. The inner end of biasing element 60 is formed with a generally inturned or internally projecting flange 72 adapted to contact the surface of workpiece tube 70 which passes through it. Inside workpiece tube 70 is a mandrel 74 which in the embodiment illustrated is stepped to provide reduction of internal diameter as well as reduction of wall thickness in workpiece tube 70 as will hereinafter be described in more detail.

It will be seen that biasing element 60 is pivotably mounted, by reason of the specific design of bearing 52, so that appropriate tension or pressure on a selected arm 66 will cause the inturned flange 72 to bear against one side of workpiece tube 70 near the portion thereof being worked and plastically deformed by circular working rings 30 and 32.

The action of working rings 30 and 32 is such that pressure applied to one side of workpiece tube 70 by biasing element 60 will cause greater working action and wall thickness reduction by rings 30 and 32 at the side of tube 70 opposite to the side at which such pressure is applied. It will be understood that biasing pressure applied to a side of workpiece tube 70 will also be transmitted to mandrel 74 which is inside this tube. Working rings and 32 work and plastically deform metal of workpiece tube 78 over mandrel 74. Therefore, when mandrel 74 is biased toward a particular side of workpiece tube 70, increased working action and reduction of wall thickness of workpiece tube 70 will be obtained on that particular side. The effect can be considered to be an urging into closer spacing of mandrel 74 and the edges of working rings 30 and 32 as they travel over that side. A tube which is not perfectly concentric will have one side of thicker wall thickness than the opposite side. Thus, to improve concentricity of such an eccentric tube, pressure from the flanged end 72 of biasing element is applied to that side of workpiece tube characterized by being of lesser wall thickness than the opposite side. The greater working action between mandrel 74 and rings 30 and 32 on the opposite (thicker wall thickness) side results in a greater thinning eifect on this originally thicker wall and produces a reduced tube of improved concentricity. If it is desired to produce a tube specifically more eccentric than the starting workpiece tube 70, then an arm 66 is manipulated or tensioned so as to cause the end of biasing element 60 to bear against that side of tube 70 which it is desired to have selectively lesser reduction of its wall thickness. The finished tube will be produced having a thicker wall on the side at which such pressure is applied, the opposite side being preferentially thinned by the combined action of working rings 30 and 32 and the biasing influence of element 60.

The effect of such reduction and improvement in concentricity will be apparent from FIGS. 3 and 4. In FIG. 4 the cross section of the original workpiece tube 70 is shown and its appreciable degree of eccentricity results in a thicker wall at the top side and a thinner wall at its bottom side. In FIG. 1 outward and downward pull on top arm 66, as shown by the adjacent arrow, results in a pivoting tendency of biasing element 60 and causes flange 72 to bear and exert pressure against the bottom side of workpiece tube 70 near the portion thereof being plastically deformed by working rings 30 and 32. This biasing action causes the working rings 30 and 32 to selectively provide a greater working and thinning action on the top side of workpiece tube 70 which was originally thicker than the bottom side. The resulting effect is to improve the concentricity (or reduce the degree of eccentricity) of tube 70 at the same time that it is being reduced in over-all thickness and internal diameter, as illustrated in FIG. 3.

Use of the apparatus of this invention in operation will be more clearly understood by reference to FIG. 5. Therein is shown a tube reducing machine which comprises an elongated, heavy frame 75 which is supported by pillars 76 and 78, which are in turn supported by blocks 80 and 82. The tube reducing machine is shown broken at A and B in the drawing for purposes of conciseness. The top of frame 75 is provided with horizontal ways 84 on which travel a pair of movable dollies 86 and 88. A central member 90 is provided as part of frame 75 to which are anchored as at 92 the ends of an opposed pair of hydraulic cylinders 94 and 96. The outer ends of piston rods 98 of hydraulic cylinders 94 and 96 carry rotatable sprockets 100 in whose teeth are engaged the links of chains 102. An upper portion of one of chains 102 is connected to dolly 86 as by heavy bolt 104, an upper portion of the other chain 102 being similarly connected to dolly 88 by bolt 106. The lower parts of chains 102 are anchored to a lower member of frame 75 as at 108. Chains 102 are in effect endless, being also carried around inner sprockets which are maintained in fixed, spaced relation to sprockets 100 by bars 112. The axles of sprockets 100 are supported 4 in a generally horizontal plane by being rotatably mounted on tracks 114.

Mounted on an upper portion of frame 75 and over ways 84 is bearing member 116 provided with bearing 118 which rotatably supports hollow shaft 38. The end of shaft 38 is fixedly attached to one end of frame 10 of the working ring assembly as previously described, the other end of shaft 38 being fixedly attached to bevel gear 120. Meshing with bevel gear 120 is pinion gear 122 which in turn is fixedly mounted on shaft 124 of electric motor 126.

Securely mounted on dollies 86 and 88 are grip members 128 and 130 respectively. These grip members may be of conventional jamming wedge design, grip member 130 being adapted to grip a workpiece tube 70 being fed into the tube reducing tool and grip member 128 being adapted to grip a finished tube 132 which constitutes the workpiece tube 70 after passage through and reduction by the reducing tool.

During working or reducing of workpiece '70 over mandrel 72, a considerable amount of heat is generated and efficient working and reducing action depends at least in part in maintaining a substantially uniform and proper temperature in the portion of the workpiece tube 70 being worked and reduced. To accomplish this a supplied from resev oirthrough 136 through pump 138, uniform elevated temperature, is supplied to mandrel 72 by pipe 134 to which it is connected and to which oil is supplied fror reservoir trough 136 through pump 138, supply pipe 140 and swivel connection 142. Valve 144 is placed in pipe 140 so that the flow of oil therethrough can be controlled, and electric immersion heatiing element 146 is placed in trough 136 so that the temperature of the circulating oil may be raised initially and used if necesary to maintain the oil at an elevated temperature. The flow of oil around its circuit will result in appreciable cooling thereof which may be supplemented by conventional means if desired. Auxiliary pipeline 148 is connected to supply pipe 140 to lead a spray or jet of oil to the exterior surface of the workpiece. During operation the end of auxiliary pipe 148, leading through the interior of hollow shaft 118, supplies oil in close proximity to the outside of the portion of the workpiece tube 70 actually being worked. The oil circulation system assists in maintaining the workpiece tube 70, the circular working elements 30 and 32 of the apparatus, and the mandrel 72 at the desired elevated temperature, and at the same time provides lubrication for the working action. It may provide heating or cooling of the oil as necessary.

Hydraulic cylinder 94, which comprises the means for applying tension to draw the end of reduced tube 1 3 2 through the tube reducing tool, is provided with a supply of oil under pressure from pump 150 through pipe 152 which is provided with gauge 154. A drain line 15 6 is provided which returns oil from the other end of cylinder 94 into reservoir 158. Fouraway valve is provided and is connected to pipes 1152 and 1 56 so that the direction of flow of oil under pressure may be reversed when desired to move dolly 86 in the opposite direction from that in which it is moved during normal operation.

Hydraulic cylinder 96, which provides means for applying back tension to workpiece tube 70 during reduction thereof, is supplied with oil from pump 162 through pipe 164 which is provided with gauge 166. A drain line 168 is provided from the other end of cylinder 96 which leads also into reservoir 158. Four-way valve 170 is connected to pipes 164 and 168 so that the direction of oil flow under pressure may be reversed into cylinder 96 to .move dolly from left to right in FIG. 5, if desired, and when the machine is not operating to reduce tubing. Pipe 164 communicates with a bypass pipe 172 which is provided with valve 174 and also relief valve 176 from which oil may drain back into reservoir 158 through pipe 178. The pressure in the left hand end of cylinder 96 can be maintained at any predetermined value by adjusting the oil by-pass through relief valve 176. The function of cylinder 94 is to provide force to draw tube 132 through the working rings 30 and 32 while the function of cylinder 96 is to exert a back tension or braking effect. During tube reducing operation oil pressure is maintained in the left hand end of cylinder 96 by pump 162 with valve 174 open and the pressure maintained at a predetermined value by relief valve 176. While the oil pressure thus maintained urges the piston in cylinder 96 in the direction from left to right in FIG. 5, this force is overcome by the greater force exerted by cylinder 94 in drawing the workpiece tube 70 through the working rings 30 and 32, and dolly 88 moves from right to left.

Biasing action by the flange end 7 2 of element 60 may be accomplished by manual tension or pressure on a selected arm 66 of ring 64. Preferably, however, and in order to maintain a uniform bias pressure which will result in more uniform eccentricity control, adjustable inechanical means to provide tension are arranged to maintain the required tension on a selected one of the arms 66. To accomplish this, a series of hooks 180 are arranged =welded, or other-wise fastened to the stationary end surface of bearing member 116 so that into one or more if desired of these hooks 18 0 can be attached the end of an elongated spring 162 whose other end is passed through or otherwise connected to threaded shaft 184. Arms 66 near their outer ends are provided with holes through which the end of threaded shafts 184 are passed and Wing nuts 18 6 are threaded onto shafts 184 so that the tension on arm 66 may be adjusted to produce the desired eccentricity variation effect.

In operation of the apparatus described and illustrated, the Working rings 30 and 32 are first adjusted to provide the required reduction in the outside diameter of workpiece tube 70. This is accomplished by appropriate rotation of inner ring frames 16 and 16 and setting these in their adjustment by tightening set screws 24. The workpiece tube 70 is pointed (by any convenient and known method) and the pointed end passed through the working rings 30 and 32 and gripped by grip 1'28 on dolly 86. The feed end of workpiece tube 70 is gripped by grip 1 30 on dolly 88 at any convenient point along its length. A mandrel 74, of design to accomplish the required reduction, which in the apparatus illustrated is of stepped configuration, is threaded onto pipe 134 and inserted into the workpiece tube 70 so that its shoulders are in working alignment with the corresponding Working edges of working rings 30 and 3 2. Connection of pipe 134 with swivel 142 is necessary to allow mandrel 74 to freely rotate within workpiece tube 70 during reduction thereof. Heater 146 is then turned on to heat the oil in reservoir trough 136 and pump 138 is started to circulate hot oil through mandrel 74 and also to the outside surface of the workpiece tube 70 and working rings 30 and 32, through pipe 148. When the temperature of these elements has been sufficiently raised, and for example, when reducing titanium tubing, a circulating oil temperature of preferably between 200 and 300 F. will be advantageous, motor 126 is started to rotate the working ring assembly around the workpiece tube 70. Pump 150 is started to actuate hydraulic cylinder 94 to draw the finished reduced tube 132 through the working rings 30 and 32 while they are travelling around the circumference of workpiece tube 70, and pump 162 is operated and relief valve 176 is set to maintain back tension, exerted by cylinder 96, on workpiece tube 70. The setting of the hydraulic system valves during operation is as shown in FIG. 5. During operation the circulating oil is maintained at substantially uniform elevated temperature by adjustment of heater 146 and valve 144.

As the workpiece tube 70 is drawn through the working rings 30 and 32, while the outer frame of the Working ring assembly is being rotated by motor 126, the working rings 30 and 32 progressively work the metal of the workpiece tube 70 over mandrel 74 as they travel around its circumference by an action which plastically deforms the metal of workpiece tube 70, causing the metal to flow generally laterally out from under the working edges of the working elements 30 and 32 in a direction generally parallel to the longitudinal axis of workpiece tube 76. At the same time outward and downward pressure is exerted on the top of arm 66 generally in the direction of the arrow shown in FIG. 1 in order to cause the inturned flange 72 of biasing element 60 to exert pressure and bear against the bottom and thinner side of workpiece tube 70 and also on the same side of mandrel 74. Alternatively and preferably such pressure may be exerted by mechanical means such as spring 182 which exerts appropriate tension toward the bearing member 166 on the bottom arm 66 as shown in FIG. 5 and this tension is regulated and maintained by tightening wing nut 186 on threaded rod 184. It will be appreciated that the inward tension maintained by the spring arrangement on the bottom arm 66 as shown in FIG. 5 produces equivalent effect on the biasing element 60 as manually applied pressure on top arm 66 as described with respect to FIG. 1. The mechanically applied tension results in maintenance of more uniform biasing effect during tube reduction. The working action produces a reduced tube 132 corresponding in internal diameter to the diameter of the small end of mandrel 74 and of wall thickness determined by the spacing between the working edges of Working ring 30 and the outside surface of the small end of mandrel 74 aligned with it. The result of the biasing effect produced by element 60 with its inturned flange 72 bearing against the bottom side of workpiece tube 70 is to cause greater wall thickness reduction action by working rings 30 and 32 as they travel around the top side of workpiece tube 70. The combined result of the working action between working rings 30 and 32 and mandrel 74 under the influence of the biasing effect exerted as hereinbefore described, is to improve the concentricity of an original eccentric workpiece tube 70 as illustrated in FIG. 4 to produce a more concentric reduced tube 132 whose cross-section is illustrated in FIG. 3.

After reduction of workpiece tube 70 over its length (except for a necessary gripping portion at each end) rotation of the working ring assembly is stopped, oil circulating pump 138 is shut down, hydraulic cylinder pumps and 162 are shut down, mandrel 74 is removed by separating pipe 134 and swivel 142 conveniently from pipe 140 where they are joined by a union, and the ends of workpiece tube 70 and finished tube 132 are removed respectively from grips 130 and 128. The finished tube 132 is then withdrawn and may be further processed by separation of point and workpiece stub ends, and any further finishing desired. Dollies: 86 and 83 are then repositioned by suitable adjustment of four-way valve and closing of valve 174 so that oil may be pumped into the required ends of cylinders 94 and 96. The operation may then be repeated to produce another length of tube.

The speed of rotation of the assembly carrying working rings 30 and 32 will vary according to the type of metal being reduced, the degree of reduction and other factors. The amount of tension applied to arm 66 to provide sufiicient biasing effect to result in the desired change of concentricity in the workpiece tube will also vary additionally according to the amount of eccentricity correction required or the degree of eccentricity imparted to the finished tube. Generally speaknig, the tension required is not very great and it is postulated that the intensive working effect of working rings 30 and 32 as they travel around the outer circumference of workpiece tube 70, is such that a relatively light biasing pressure will cause sufiicient circumferential displacement of metal to result in a substantial change in the concentricity of the workpiece tube as it is drawn progressively through working rings 30 and 32.

While the biasing element 60 and its associated supporting and actuating mechanism has been shown at the feed end of the working ring assembly, that is, the end at which the workpiece tube 70 enters, it may also be placed at the other end, that is, the end from which finished tube 132 is withdrawn, if desired. It is only necessary that the biasing effect be applied to the tube near that portion of the tube being plastically deformed, so that related biasing effect on the mandrel inside the tube and in the area of the working rings may be obtained.

The mandrel in the tube reducing machine will be of type and configuration to produce the reduction intended. If reduction of both wall thickness and internal diameter is desired, the mandrel will be of stepped design as shown in FIG. 1. If wall thickness reduction only is desired the mandrel will comprise a uniform outside diameter cylindrical element over which the metal of the tube is plastically deformed. The apparatus and method of this invention will be effective to change or vary the concen tricity of the tube with either type of mandrel.

The apparatus and method of this invention are useful to change the concentricity of a metallic tube being reduced in wall thickness, internal diameter or both. Thus, a tube blank or workpiece which is of poor concentricity, that is, appreciably eccentric, may be processed to produce a more concentric tube. As described hereinbefore the concentricity change is accomplished at the same time that the tube is being reduced. Additionally, the concentricity change may be toward greater eccentricity if such is desired for some specific purpose. Thus, a more or less concentric tube may be processed to produce a substantially eccentric one with a side wall appreciably thicker than its opposite side.

I claim:

1. A tube forming apparatus comprising: a mandrel supported at one end and having an outer bearing surface adapted to control the inner diameter of a tube worked thereover, outer working means having tube working surfaces adapted to press inwardly toward said mandrel around the outer surfaces of said tube when fed thereover, and biasing means comprising a biasing element separate and distinct from said mandrel and from said outer working means, and means mounting said biasing element for direct engagement with the outer surface of a tube passing through said tube working means at a point separate from but in close positional relationship to said outer working means, said mounting means being arranged to cause said biasing element to exert greater pressure along one side of said tube than along its opposite side.

2. A tube forming apparatus comprising: an elongated mandrel supported solely at one end thereof and having an outer bearing surface which controls the inner diameter of a tube worked thereover, a plurality of outer tube working surfaces rotatable about axes parallel to and offset from the axis of said mandrel, said Working surfaces being mounted to roll about and to press inwardly against said tube passing over said mandrel to cause plastic deformation and lateral flow in said tube, and biasing means comprising a tubular bias element mounted generally coaxially with said mandrel and having an inner diameter greater than the working diameter of the side of said outer working means facing said tubular bias element, the end of said tubular bias element farthest from said outer working means being mounted to pivot about a further axis perperdicular to the axis of said man-drel and means for applying a force to pivot said bias element about said further axis whereby it engages and presses on one side of the outer surface of tubes passing therethrough and through said outer working means.

3. A tube forming apparatus comprising: an elongated mandrel support-ed solely at one end thereof and having an outer bearing surface which controls the inner diameter of a tube worked thereover, an outer tube surface working means including a frame member mounted for rotation about an axis in general alignment with the axis of said mandrel and further including a plurality of hollow circular tube working elements having peripheral working surfaces mounted for rotation in said frame about axes parallel to and offset from the rotational axis of said frame, said frame being located such that said peripheral working surfaces press inwardly toward said mandrel about and against the outer surfaces of tubes passing over said mandrel and plastically deform such tubes, a bearing assembly having arcuate races permitting relative movement between races about secondary axes perpendicular to the normal rotational axis of said hearing, the outer race of said bearing assembly being attached to said frame member in coaxial alignment with its said normal rotational axis, a tubular biasing element attached at one end to the inner race of said bearing assembly and extending toward said outer tube surface working means, said tubular biasing element having an inner diameter larger than the working diameter of the side of said outer tube working means facing said biasing element, and resilient means connected to maintain a pivotal force upon said tube biasing element about one of said secondary axes whereby it maintains a bias pressure on one side of the outer surface of tubes passing over said mandrel and through said outer tube surface working means.

A tube forming apparatus comprising: a mandrel supported at one end and having an outer bearing surface adapted to control the inner diameter of a tube Worked thereover, outer working means having tube Working surfaces adapted to press inwardly toward said mandrel around the outer surfaces of said tube when fed thereover, and biasing means comprising a biasing element separate and distinct from said mandrel and from said outer working means, and means mounting said biasing element for direct engagement with the outer surface of a tube passing through said tube working means ata pomtseparate from but in close positional relationsh p to said outer working means, said mounting means being arranged to cause said biasing element to press inwardly upon the surface of said tube in a given radial direction.

5. A tube forming apparatus comprising: an elongated mandrel supported solely at one end thereof and having an outer bearing surface adapted to control the inner diameter of a tube worked thereover, outer working means having tube working surfaces adapted to press inwardly toward said mandrel around the outer surfaces of said tube when fed thereover, andbiasing means comprising a biasing element separate and distinct from said mandrel and from said outer working means, and means mounting said biasing element for direct engagement with the outer surface of a tube passing through said tube working means at a point separate from but in close positional relationship to said outer working means, said mounting means being arranged to cause said biasing element to exert greater pressure in a given radial direction against one side of said tube.

6. A tube forming apparatus comprising: an elongated mandrel supported solely at one end thereof and having an outer bearing surface which controls the inner diameter of a tube worked thereover, outer working means having tube working surfaces adapted to press inwardly toward said mandrel around the outer surfaces of said tube when fed thereover, and biasing means comprising a biasing element separate and distinct from said mandrel and from said outer working means and means mounting said biasing element for direct engagement with the outer surface of a tube passing through said tube working means at a point separate from but in close positional relationship to said outer working means, said mounting means including resilient means connected to maintain a continuous force urging said biasing element against said tube in a givsn radial direction.

References Cited by the Examiner UNITED STATES PATENTS Davis 82-702 Amberg 11353 Sanders 2058 10 W 10/1961 Poncar 2057 12/1961 Russel 2057 7/1962 Le Fiell 113--53 5/1964 Hill et a1. 2057 FOREIGN PATENTS 10/1957 Great Britain.

CHARLES W. LANHAM, Primary Examiner. Kessler 205-8 RICHARD H. EANES, Examiner. 

1. A TUBE FORMING APPARATUS COMPRISING: A MANDREL SUPPORTED AT ONE END AND HAVING AN OUTER BEARING SURFACE ADAPTED TO CONTROL THE INNER DIAMETER OF A TUBE WORKED THEREOVER, OUTER WORKING MEANS HAVING TUBE WORKING SURFACES ADAPTED TO PRESS INWARDLY TOWARD SAID MANDREL AROUND THE OUTER SURFACES OF SAID TUBE WHEN FED THEREOVER, AND BIASING MEANS COMPRISING A BIASING ELEMENT SEPARATE AND DISTINCT FROM SAID MANDREL AND FROM SAID OUTER WORKING MEANS, AND MEANS MOUNTING SAID BIASING ELEMENT FOR DIRECT ENGAGEMENT WITH THE OUTER SURFACE OF A TUBE PASSING THROUGH SAID TUBE WORKING MEANS AT A POINT SEPARATE FROM BUT IN CLOSE POSITIONAL RELATIONSHIP TO SAID OUTER WORKING MEANS, SAID MOUNTING MEANS BEING ARRANGED TO CAUSE SAID BIASING ELEMENT TO EXERTED GREATER PRESSURE ALONG ONE SIDE OF SAID TUBE THAN ALONG ITS OPPOSITE SIDE. 